This invention relates to a method for monitoring de-stabilizing electrical events in an electrical power grid including a plurality of power lines interconnected to form the grid and to a monitoring unit for use in the method.
Equipment for monitoring the operation of an electrical power grid has been available for many years. The electrical power grid includes a plurality of electrical power transmission lines which are interconnected to supply power from a plurality of power sources to a plurality of power users. The grid interconnects power from a number of different sources to protect against blackouts due to individual failures. The grid includes transmission lines which accommodate different routings of the power again to avoid blackout due to damage to or failure of individual power transmission lines or transmission components.
Computer models of the grid or network are used to predict the response of the complete grid or network to individual failures or events. Great care is taken to attempt to avoid extensive or catastrophic failure leading to a wide reaching blackout. However such events do occur and are triggered by individual failures which then escalate if remedial action is not taken in good time.
Monitoring units are available for monitoring the individual power transmission lines. Such a unit is available from APT Power Technologies of Winnipeg, Manitoba, Canada under the trademark xe2x80x9cTESLAxe2x80x9d and a description of this intelligent electronic device is well known to one skilled in the art.
This monitoring unit includes conventional transducers which are responsive to the voltage and current on the transmission line and provide an input to a processor of the monitoring unit for storage in a memory. Communication of data from the monitoring unit to a central recording station can be effected.
The individual monitoring units include algorithms which allow detection and recording of dynamic events that are evident at the point on the power grid to which the unit is connected.
However these individual monitoring units do not provide a system which allows the managers of the network to determine the effect of events over a wide range of the network.
It is one object of the present invention therefore to provide an improvement to a conventional monitoring system which allows the response of the wide area of the grid to a de-stabilizing event to be monitored.
According to one aspect of the invention there is provided a method for monitoring de-stabilizing electrical events in an electrical power grid including a plurality of power lines interconnected to form the grid comprising:
providing a plurality of independent monitoring units located at separate locations in the electrical power grid;
each unit having inputs for receiving signals related to sampled values of voltage and current on a respective one of the power lines of the grid;
each unit having a clock input indicative of a current time;
each unit having a memory for storing data over a period of time related to the sampled values of voltage and current on the respective power line in association with the current time, as the values vary during the time period;
providing in each unit a processor responsive to the input signals and configured to recognise a de-stabilizing electrical event;
providing a central station arranged for communication to and from each of the units over a communication medium;
when a de-stabilizing electrical event is recognized by one of the units at an event time, causing that unit to communicate to the central station the event time and a trigger command;
when the central station receives the event time and the trigger command, causing the central station to communicate over the communication medium to each of the units the trigger command and the event time;
the trigger command at each unit causing a record to be created and stored on the unit of the data at the event time;
and causing the central station to collate the data for the event time from each of the units in its own database.
Preferably the communication medium is non-dedicated and can be provided by conventional phone lines using a data modem for communication of the data, or may be provided by the internet, satellite communication or other suitable medium.
Preferably the method includes providing at least one additional separate central station each having associated therewith a plurality of units and arranging the central stations such that when one central station receives the event time and the data, is caused to communicate over the communication medium to the additional central station for communication to each of the units associated with the additional central station a the trigger command and the event time.
Preferably the clock input is obtained from GPS.
Preferably the memory of each unit is a continuous circular memory arranged to store data over a time of the order of ten to thirty minutes .
According to a second aspect of the invention there is provided a monitoring unit for monitoring de-stabilizing electrical events in an electrical power grid including a plurality of power lines interconnected to form the grid comprising:
a monitoring processor arranged to be located at a respective one of a plurality of separate locations in the electrical power grid;
inputs for receiving signals related to sampled values of voltage and current on a respective one of the power lines of the grid;
a clock input for providing a signal indicative of a current time;
a memory for storing data over a period of time related to the sampled values of voltage and current on the respective power line in association with the current time as the values vary during the time period;
an output arranged for communication to and from a central station over a communication medium;
the processor being arranged to be responsive to the input signals for recognizing a de-stabilizing electrical event and, when a de-stabilizing electrical event is recognized by the unit at an event time, to communicate via the output to the central station the event time and a trigger command;
and the processor being arranged, when receiving via the output from the central station a trigger command and an event time, to store in the memory of the unit data in association with that event time.
The invention as defined above therefore provides a recording system that can capture data on the response of an electrical power system over a wide geographical area to de-stabilizing electrical events and ensures recordings from all recording points at the time of the event by issuing cross-triggers via the central station. The captured data can be obtained from multiple recording locations and is automatically time-synchronized so that an overall coordinated snapshot of the power system dynamics is achieved. The wide-area capture is achieved through standard Internet, Intranet, and/or switched telephone network communication links.